This invention concerns the brake apparatus for a train made up by the connection of a number of transit-type railway vehicles, and aims at the simplification of the braking apparatus, reduction of the size and weight of the apparatus, improvement of the brake capacity, simplification of the installation, and reduction of cost. In transit-type trains of the past, braking gear has been used, such as shown in the prior art of FIG. 1, for example. That is to say, the electric brake command sent out from the brake controller 1 installed on the driver's stand is fed to the command wires SB.sub.1, SB.sub.2, and SB.sub.3, which are connected to extend throughout all the vehicles, each command wire transmitting a control signal to a respective one of the electro-pneumatic valves 2, 3, and 4 installed on each vehicle. These electro-pneumatic valves 2, 3 and 4 are operated by reception of the on-off binary electric signal from the command wires SB.sub.1, SB.sub.2 and SB.sub.3, in order to control the supply and exhaust of fluid pressure supplied to the respective diaphragm plate chambers C.sub.1, C.sub.2 and C.sub.3 of the double relay valve 5. The output pressure PB reflects these combined pressure signals and is connected to the brake cylinder BC. For example, if the digital binary signals sent to wires SB.sub.3, SB.sub.2 and SB.sub.1 are expressed in terms of binary codes (0 0 1), (0 1 0), (0 1 1), (1 0 0), (1 0 1), (1 1 0), and (1 1 1), and if the proportion of three diaphragm plate areas of relay valve 5 is 7:6:4, output pressures in seven stages, as shown in the table below, are formed and sent to the brake cylinder BC.
______________________________________ Digital Condi- Electro- Pressurized Weighted tion of Command Pneumatic Relay Valve Values of Wires SB.sub.3, SB.sub.2 Valves Diaphragm Output and SB.sub.1 which open Chambers Pressures ______________________________________ 0 0 1 2 C.sub.1 1 0 1 0 3 C.sub.2 2 0 1 1 2, 3 C.sub.1, C.sub.2 3 1 0 0 4 C.sub.3 4 1 0 1 2, 4 C.sub.1, C.sub.3 5 1 1 0 3, 4 C.sub.2, C.sub.3 6 1 1 1 2, 3, 4 C.sub.1, C.sub.2, C.sub.3 7 ______________________________________
The compressed air supplied to the previously mentioned electro-pneumatic valves 2, 3 and 4 is adjusted to a pressure corresponding to the load of each vehicle by the load-adaptive pressure regulator valve 6. The load-adaptive regulating valve is connected at its diaphragm chambers 6a and 6b respectively to the air springs AS.sub.1 and AS.sub.2 in a vehicle. These diaphragm chambers 6a and 6b are compartmentalized by a pair of diaphragms linked with a connecting rod. An exhaust chamber 6c adjoining chamber 6b contains a spring 6e, which acts upwardly on a supply-exhaust valve rod 6f through a diaphragm plate 6d installed in the exhaust chamber 6c. A supply-exhaust valve 6g is normally engaged with a supply seat and disengaged from an exhaust seat formed at the end of rod 6f. Compressed air supplied via input 6h is delivered to output 6i via the supply-exhaust valve 6g proportional to the mean of the two pressures of the air springs AS.sub.1 and AS.sub.2. Accordingly, the braking pressure corresponding to the command from the brake controller 1, as well as the load of each vehicle, is developed independently and supplied to the brake cylinder of each vehicle. According to the above brake apparatus, each vehicle is equipped with a control unit consisting of the electro-pneumatic valves 2, 3 and 4, the multi-diaphragm relay valve 5, and the load-adaptive regulating valve 6, all being conventional. However, for the sake of simplification and weight reduction, a method has been devised, in which the control unit and the load-adaptive regulating valve are installed only in one vehicle, but not in the other vehicles. For example, it is uneconomical and not conducive to weight reduction and simplification to attach the same brake apparatus to relatively small size vehicles such as vehicles for monorails or for the new light rail vehicles in the same way as for suburban trains or subway trains. In order to meet this need, a method is being used in which by installing the controlling unit and the load-adaptive regulating valve 6' in one car (Car A) and only the relay valve 7 in the other cars (for example, Car B), the braking pressure is sent to the brake cylinder of the other car (Car B) from the output pressure of the control unit of one car (Car A). The relay valve 7 is a commonly known self-lapping type. Weight reduction and cost reduction are achieved by this method in small vehicles, since only one set of the control unit and the load-adaptive regulating valve is used. However, with this arrangement, it is necessary to install a large number of pipes, which are connected between cars to transmit the air spring pressure of each vehicle to the load-adaptive regulating valve 6' of Car A, making the fitting of the components complex. Besides, since the single load-adaptive regulating valve transmits to the control unit the mean pressure of the air-spring pressure of all the vehicles, a braking force best suited to the load condition of each vehicle cannot be obtained when the load weight differs for each vehicle. This causes severe interaction between the vehicles. In light vehicles, an unnecessarily large braking force results in wheel slippage, while the brake effect is inadequate on loaded vehicles.